Is valve float the fact that the valves can't close fast enough?

Yes he does. So what? Doesn't matter. No it's not.

How can the landlord plausibly argue that he did not know they are a cannabis business? He either leased to them knowing they are a cannabis business, or continued to lease to them when he found out. The underlying contract most likely acknowledges what the premises are going to be used for.

Your failure to appreciate what laws are being broken is not a defense to the clear illegality of the of what they are doing.

Yeah it's an interesting choice for sure.

Jurisdiction has nothing to do with it but nice try. They are not challenging jurisdiction, rather the enforceability of the contract. The legal reasoning is perfectly sound but the problem is they are inviting a raid from the feds when you admit in federal court that you are operating an illegal business.

The feds have said they won't bother dispensaries that are only breaking weed laws*,* but there's still no legal reason they couldn't change their minds, and the defense they are asserting to the contract invites some analysis as to whether it may constitute some type of real estate fraud or something else that might qualify for federal intervention even under existing policy.

If the contract is for something illegal, the feds are not going to enforce it. Knowingly renting out a property for purposes of cannabis production or sale violates any number of federal laws. The landlord's actions make him guilty of conspiracy to produce/traffic marijuana. It would be the same as asking a federal court to enforce a contract for murder-for-hire.

The real problem for the tenant is that they are risking a federal crackdown. If they're going to affirmatively claim their business is illegal in federal court there's really no reason the feds shouldn't come in and shut them down.