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.