BOTSFORD, J.

We consider here for the first time the Commonwealth's new medical marijuana law, "An Act for the humanitarian medical use of marijuana," St. 2012, c. 369 (act), which the voters approved in November, 2012.1 The central question presented is whether, with the act in effect, police may obtain a search warrant to search a property where they suspect an individual is cultivating marijuana by establishing probable cause that cultivation is taking place or are required to establish probable cause to believe that the individual was not registered, or licensed, to do so. In accord with cases relating to other types of license regimes, we conclude that, if police seek a warrant to search such a property for evidence of illegal marijuana possession or cultivation, they must offer information sufficient to provide probable cause to believe the individual is not properly registered under the act to possess or cultivate the suspected substance. In this case, a judge in the District Court allowed the defendant's motion to suppress evidence seized by police during a search of the defendant's property conducted pursuant to a warrant in May of 2013, after the act went into effect. We agree with the motion judge that the affidavit filed in support of the search warrant application demonstrated probable cause that the defendant was cultivating marijuana at the property, but that, in light of the act, the affidavit failed to establish probable cause to believe that the defendant was not authorized to do so and therefore was committing a crime. We affirm the order allowing the motion to suppress.2

Background. On May 30, 2013, a three-count complaint issued from the Orleans Division of the District Court Department charging the defendant, Josiah H. Canning, with possession with the intent to distribute marijuana, G. L. c. 94C, § 32C (a); distribution of marijuana, G. L. c. 94C, § 32C (a); and conspiracy to violate the drug laws, G. L. c. 94C, § 40.3 The complaint's issuance followed a search of the defendant's property in Brewster conducted May 30, 2013, pursuant to a search warrant issued on May 29. The affidavit submitted by Detective Christopher Kent of the Yarmouth police department in support of the warrant application recited the following facts.

During the week of May 19, 2013, Kent met with a confidential informant, who told Kent that the owner of certain property in Brewster (property) — whom Kent later determined from town records to be the defendant — and another male were involved in an indoor "marijuana grow" operation located at the property.4 On May 21, Kent and another detective observed the property from a nearby driveway, and noticed that windows of the addition to the house on the property were obscured by dark material, saw an aluminum flexible hose protruding out of one of the windows, and also observed a pickup truck registered to the defendant in front of the house. On May 24 and 28, Kent and one or more additional police officers returned to observe the property; on both occasions, they smelled a strong odor of "freshly cultivated" marijuana emanating from the house, noticed the aluminum hose coming out of the window of the addition, heard the sound of fans, and, using night vision goggles, saw light emanating from another window. Also on May 28, Kent was provided information from a police officer in another town that that officer previously had observed the defendant and another man purchasing "a large amount of indoor [marijuana] grow materials" from a "hydroponic shop" in Foxborough and then loading the materials into an automobile registered to the defendant. On May 29, Kent obtained utility bills relating to electrical service for the property and neighboring homes on Main Street in Brewster. These records revealed that for the previous six months, the average kilowatt usage for three neighboring homes was 542.3 kilowatt hours (kWh), 23.3 kWh, and 246.6 kWh, respectively; the average kilowatt usage for the defendant's property for the same time period was 3,116.5 kWh. Based on his training and experience, Kent was aware that because marijuana growing operations require different types of electrical equipment, e.g., "high intensity discharge lamps, fluorescent lights, fans, reflectors, irrigation and ventilation equipment such as aluminum flexible hose" to be operating consistently, high usage of electricity — a "noticeable increase in kilowatt usage" — is to be expected.

When the police executed the search warrant that, based on the affidavit, a judge in the District Court had issued, the defendant was present. Seized during the search, among other items, were seventy marijuana plants, eleven fluorescent industrial lights, an aluminum flexible hose, a digital scale, approximately 1.2 pounds of marijuana, and $2,697. The defendant was placed under arrest.

The defendant filed a motion to suppress the seized evidence, and also to suppress statements he made at the time of the search and his arrest. A different District Court judge allowed the motion in a written memorandum of decision. The judge concluded that the search warrant affidavit "establishe[d] probable cause that marijuana was being cultivated indoors at the defendant[']s home," but concluded in substance that in light of the act, the affidavit failed to establish probable cause that the cultivation was for more than a sixty-day supply of marijuana or that the defendant was not authorized to grow that amount — and therefore that the cultivation was illegal. The Commonwealth filed a timely application for leave to file an interlocutory appeal of the judge's suppression order and motion to stay further proceedings in the case. See Mass. R. Crim. P. 15 (a) (2), as appearing in 422 Mass. 1501 (1996). A single justice of this court allowed the application and reported the case to the Appeals Court. Thereafter, we allowed the Commonwealth's motion for direct appellate review.

Discussion. 1. Overview of the act. The voters approved the act as a ballot measure in 2012, and the act went into effect on January 1, 2013. St. 2012, c. 369. Section 1 of the act sets out a statement of purpose:

The term "medical use of marijuana" is defined in the act as follows:

St. 2012, c. 369, § 2 (I). The substantive provisions of the act that follow the definitional section first set out the parameters of protection from State prosecution and penalties that the act respectively gives to physicians and health care professionals, qualifying patients and their personal caregivers, and licensed dispensary agents. See id. at §§ 3-5.5 See also id. § 6 (A) ("The lawful possession, cultivation, transfer, transport, distribution, or manufacture of medical marijuana as authorized by this law shall not result in the forfeiture or seizure of any property"). These provisions are followed by a section specifying "limitations" of the act, including the following: "Nothing in [the act] supersedes Massachusetts law prohibiting the possession, cultivation, transport, distribution, or sale of marijuana for nonmedical purposes." Id. at § 7 (E). Thereafter, the act establishes a medical marijuana registration or licensing regime that is to be set up and administered by the Department of Public Health (department), and that covers nonprofit medical marijuana treatment centers, medical marijuana center dispensary agents, and qualifying patients and personal caregivers. See id. at §§ 9-12. Under the act, it is clear that the principal source of medical marijuana is intended to be the nonprofit medical marijuana treatment centers, or dispensaries, that are to be registered by the department. See id. at §§ 2 (H), 9 (B), (C). To that end, the act directed that during the first year the act was in effect, the department "shall" have registered up to thirty-five of these centers, with at least one in every county, and further states that "[i]n the event the [d]epartment determines in a future year that the number of treatment centers is insufficient to meet patient needs, the [d]epartment shall have the power to increase or modify the number of registered treatment centers." See id. at § 9 (C).

Of particular relevance here are the act's provisions relating to qualifying patients and personal caregivers as well as to hardship cultivation registrations. A "qualifying patient" is defined as "a person who has been diagnosed by a licensed physician as having a debilitating medical condition." St. 2012, c. 369, § 2 (K). The act requires a qualifying patient or a personal caregiver6 to obtain from the department a "registration card," which is a personal identification card issued by the department that serves both to "verify that a physician has provided a written certification to the qualifying patient," and to "identify for the [d]epartment and law enforcement those individuals who are exempt from Massachusetts criminal and civil penalties for conduct pursuant to the medical use of marijuana." Id. at § 2 (L). See id. at § 12 (describing application requirements for medical marijuana registration card for qualifying patients and personal caregivers). A qualifying patient or his or her personal caregiver is permitted to possess up to a sixty-day supply of marijuana necessary for the patient's personal medical use. See id. at § 4 (A). In addition, a qualifying patient whose access to a licensed medical marijuana treatment center is limited by finances or an inability to travel to a licensed center may obtain a "hardship cultivation registration" that allows the patient or the patient's personal caregiver to cultivate a suffcient number of marijuana plants to produce and maintain a sixty-day supply of marijuana. Id. at § 11. The act tasks the department with defining "the quantity of marijuana that could reasonably be presumed to be a sixty-day supply for qualifying patients." Id. at § 8.7

The act provides that the department was to issue regulations to govern implementation of all the registration provisions in the act. St. 2012, c. 369, § 13. These regulations were to be published within 120 days of the act's effective date, May 1, 2013. The act also provides, however, that "[u]ntil the approval of final regulations, written certification by a physician shall have constituted a registration card for a qualifying patient." Id. See id. at § 2 (N) (definition of "written certification"). Additionally, until final regulations were in place, "the written recommendation of a qualifying patient's physician shall have constituted a limited [i.e., hardship] cultivation registration." Id. at § 11.8

The department issued its final medical marijuana regulations on May 8, 2013. 105 Code Mass. Regs. §§ 725.000 (2013). But of significance to the present case, § 725.015 of these regulations, which defines the registration requirements for a qualifying patient, provides that if a qualifying patient received an initial written certification signed by a physician before the department was accepting registration applications, "the initial certification will remain valid until the application for the registration card is approved or denied by the [d]epartment."9 The same holds true for limited cultivation registrations: a qualifying patient who received written certification from a physician is entitled to continue to use that written certification as a hardship cultivation registration "until the application for the hardship cultivation registration card is approved or denied by the [d]epartment." 105 Code Mass. Regs. § 725.035(L) (2013). The parties do not dispute that at the time of the search of the property, the department was not yet approving or denying any applications for registration, and there were no registered medical marijuana treatment centers in operation.10 Thus, a qualified physician's written recommendation, undocumented in any database, sufficed as both a medical marijuana registration card and a limited medical marijuana cultivation registration.

2. Search warrant and application. "Our inquiry as to the sufficiency of the search warrant application always begins and ends with the four corners of the affidavit.... The magistrate considers a question of law: whether the facts presented in the affidavit and the reasonable inferences therefrom constitute probable cause.... [W]e determine whether, based on the affidavit in its entirety, the magistrate had a substantial basis to conclude that a crime had been committed, ... and that the items described in the warrant were related to the criminal activity and probably in the place to be searched" (quotations and citations omitted). Commonwealth v. O'Day, 440 Mass. 296, 297-298 (2003). See Commonwealth v. Donahue, 430 Mass. 710, 711-712 (2000).

The Commonwealth contends that Kent's affidavit established probable cause for the search because, as the motion judge concluded, the affidavit provided probable cause to believe that the defendant was engaged in cultivating marijuana at the property, and in the Commonwealth's view all-or-any cultivation of marijuana remains illegal even under the act. To the extent that the act permits a limited class of properly licensed or registered persons to grow marijuana, the argument continues, the existence of a license or registration is an affirmative defense for a defendant charged with unlawful cultivation to raise at trial — the Commonwealth is not obligated to disprove such a status in order to conduct a search at the outset of an investigation.

We disagree. Although as a general matter, marijuana cultivation is a crime, see G. L. c. 94C, § 32C (a); Commonwealth v. Palmer, 464 Mass. 773, 777 (2013), and the act specifies generally that it remains so, see St. 2012, c. 369, § 7 (E), the Commonwealth is incorrect that the act has not effected any change in the statutory and regulatory landscape relevant to establishing probable cause for a search targeting such cultivation. What § 7 (E) states is that nothing in the act "supersedes Massachusetts law prohibiting the ... cultivation ... of marijuana for nonmedical purposes" (emphasis added). Under the act, cultivation of marijuana is expressly permitted if a person or entity is properly registered to do so, and the cultivation does not exceed the amount necessary to yield a sixty-day supply of medical marijuana. See St. 2012, c. 369, §§ 9 (B), (D), 11. See also id. at §§ 4-6. As previously stated, when the search at issue here took place, the act was not fully implemented; no marijuana treatment centers were operating; and therefore, pursuant to the act's express provisions, see id. at §§ 11, 13, every person who was certified as a qualifying patient or the patient's personal caregiver was authorized to cultivate a sufficient quantity of marijuana to produce a sixty-day supply — presumptively ten ounces.

In these circumstances, as the motion judge suggested, our cases involving searches for firearms that may be legally possessed with a license but are illegal in the absence of one provide an appropriate analytic framework. See Commonwealth v. Toole, 389 Mass. 159, 163 (1983).11 Accord Commonwealth v. Nowells, 390 Mass. 621, 627 (1983) (search warrant affidavit did not establish probable cause for search of defendant's apartment for illegal firearms where informants only indicated they had seen guns there: "The ownership or possession of a handgun [or a rifle] is not a crime and standing alone creates no probable cause"). See also Commonwealth v. Couture, 407 Mass. 178, 181, cert. denied, 498 U.S. 951 (1990); Commonwealth v. Stevens, 361 Mass. 868 (1972). As these cases indicate, although firearms cannot legally be carried without a license to carry, see G. L. c. 269, § 10 (a), in the absence of any evidence beyond the "unadorned fact," Couture, supra, that the defendant was carrying a gun, there was no probable cause to suspect a crime was being committed.12 Cf. Commonwealth v. Marra, 12 Mass.App.Ct. 956, 956-957 (1981) (defendant convicted of storing dynamite without license; conviction reversed where search warrant authorizing search of defendant's trailer for dynamite was not based on probable cause: "The observation of a box containing [dynamite] blasting caps, without more, to indicate that their storage was unlicensed, does not provide probable cause for entry into the [defendant's] trailer" where no circumstances set out in affidavit indicated blasting caps were, or were reasonably likely to be, unlicensed).

The Commonwealth again misses the mark in seeking to distinguish these cases and arguing that the existence of a registration card or written certification, like the existence of a license, constitutes an affirmative defense that the defendant himself is obliged to raise in the first instance — at trial. A license does constitute an affirmative defense at trial to be raised by the defendant. See G. L. c. 278, § 7.13 See also Commonwealth v. Gouse, 461 Mass. 787, 804-808 (2012); Couture, 407 Mass. at 181-182; Commonwealth v. Jones, 372 Mass. 403, 405-406 (1977). But this case is not about defenses at trial; the issue is probable cause to conduct an investigatory search. At the trial of a case in which the existence or nonexistence of a license defines whether the charged conduct was legal or instead a crime, as Couture explains, the defendant "has every opportunity to respond" by producing the license authorizing his conduct, and in the absence of the defendant's doing so, it is not unfair for the jury to presume in accordance with c. 278, § 7, that the defendant did not have a license. Couture, supra at 182. Accord Gouse, supra at 806. At the time of a search, however, such a defendant is in a very different position: the police arrive, armed with (among other things) a warrant authorizing the search; the defendant has no right to object or respond, and indeed may not even be present. Cf. Couture, supra at 182-183 (contrasting position of defendant at trial with defendant's position when confronted by police stopping defendant's truck, removing him from it at gunpoint, and conducting warrantless search of truck to locate pistol police suspected would be present). Cf. also Commonwealth v. Landry, 438 Mass. 206, 211 (2002) (charge of unlawful possession of hypodermic needle; contrasting defendant's burden to raise affirmative defense of license at trial with question whether probable cause existed for unlawful possession at time of arrest).14

The firearms and other license cases just discussed govern the result here. Beginning with the initial statement of purpose, the act's provisions make it abundantly clear that its intent is to protect the lawful operation of the medical marijuana program established by the legislation from all aspects of criminal prosecution and punishment, including search and seizure of property as part of a criminal investigation. See St. 2012, c. 369, §§ 1, 3-6. The act's medical marijuana program is structured as a licensing or registration system, and expressly contemplates the lawful possession, cultivation, and distribution of marijuana for medical purposes by a number of different individuals (and certain nonprofit entities), as long as they are registered to do so. In light of the statutory and regulatory framework created by the act, a search warrant affidavit setting out facts that simply establish probable cause to believe the owner is growing marijuana on the property in question, without more, is insufficient to establish probable cause to believe that the suspected cultivation is a crime. Missing are facts indicating that the person owning or in control of the property is not or probably not registered to cultivate the marijuana at issue.15

Detective Kent's affidavit filed in support of the search warrant in this case did not contain any information at all addressing whether the defendant was or was not registered as a qualifying patient or personal caregiver to grow the marijuana the police reasonably suspected was growing on the property.16 Nor, as the motion judge observed, did it contain other facts or qualified opinions that might supply an alternate basis to establish the necessary probable cause to believe the cultivation was unlawful. See note 15, supra. As such, the affidavit failed to establish probable cause for the search.17

We disagree with the Commonwealth that the result we reach imposes an impossible burden on police to search for elusive and difficult-to-locate information about whether a person suspected of growing marijuana is registered to do so. Although not available in 2013 when the search here was conducted, we assume that with the introduction of the electronic registration system, see note 10, supra, there is or soon will be available to law enforcement officers an accessible list of "the persons issued medical marijuana registration cards" as provided in § 15 of the act.18 Moreover, as we have suggested (see note 15, supra), information independent of registration status may also be presented to establish probable cause concerning the suspected unlawful cultivation of marijuana.

Conclusion. The order allowing the defendant's motion to suppress is affirmed.

So ordered.