The rule of law depends on lawyers. That is why, in the wake of Attorney General Jeff Sessions’ decision to rescind Obama-era policies that sidestepped the tension between federal and state laws related to marijuana, a reasonable and critical step is to ensure that lawyers can help maintain that rule of law.

The issue that confronts attorneys flows from this unusual tension between state and federal law. Regardless of state law, marijuana remains a Schedule I controlled substance under federal law, and its possession, sale or distribution remains a federal felony. Reasonable minds can, of course, disagree on whether marijuana should be illegal. Separate and apart from that public policy debate, it is very clear that the federal Controlled Substances Act (the CSA) remains the operative and supreme law of the land, and marijuana is illegal.

In general, a “lawyer shall not counsel a client to engage, or assist a client, in conduct that the lawyer knows is criminal,” a prohibition that flows from the state ethics rules. A number of states have amended or interpreted their ethical rules to specifically allow lawyers to provide “counsel or assist a client regarding conduct expressly permitted by [state] law.” These changes were intended to permit attorneys to provide counsel to assist individuals or businesses operating within the state regulatory framework governing marijuana.

But the lawyer’s obligations do not only flow from the state ethics rules. Lawyers also are, of course, subject to the criminal law. As a general matter, providing legal advice to assist somebody in committing a future crime is not only unethical, but may also constitute a criminal offense. A lawyer who, for instance, helps a money launderer set up shell companies may be joining a conspiracy to commit money laundering, and thus be subject to criminal prosecution.

In the context of marijuana, the situation is confusing. Conduct explicitly permitted by state law, and allowed by state bar ethics rules, may constitute a violation of federal criminal law. Now that the Justice Department guidance intensifies the conflict between state and federal law, it is critically important that everybody involved in state-permitted cannabis gets timely and accurate legal advice. What is needed is clear guidance on this subject to ensure that attorneys who adhere to their state ethics rules do not risk prosecution for conspiracy to violate the federal CSA.

Making this clear, and ensuring that lawyers be permitted to provide legal advice, would further a goal that both the Justice Department and those involved in state cannabis support: adherence to the rule of law. It is critical that in the present situation individuals and companies can receive competent legal advice, allowing them to understand the tension between federal and state law, and if they nevertheless determine to proceed under state law, appropriately adhere to applicable state and local law, while understanding the risks involved.

In the coming weeks, there will be increasing interest by Congress, as well as other federal agencies and departments, in responding to the Justice Department’s position. A simple first step would be for Congress to pass legislation, or the Justice Department to issue guidance, making it clear that lawyers are permitted to advise their clients in understanding the law without, themselves, facing potential criminal liability.

Steven Cash, counsel at Day Pitney in the Washington, D.C. and New York offices, is former Chief Counsel to Sen. Dianne Feinstein and former Assistant District Attorney with the New York County District Attorney’s Office.