Bad idea to ask for legal advice from anyone other than your lawyer. Yes, there can be a bust without a warrant.
Cop walks buy a house that happens to be harvesting at the time and catches a whiff of what he thinks is marijuana? There's your PC (Probable Cause) right there, and may be enough for him to be able to knock and enter the home. * But that being said, this is a rather moot point when a damn search warrant can be called in over a cell phone and approved within an hour. Even if you were made aware, I seriously doubt an hour is going to save anyone's ass, unless you've got a Government-grade oven that burns magnesium to get rid of all the "evidence". * I am not a lawyer, nor do I play one on TV. Please consult a lawyer familiar with your local laws.
Also, if a cop really wants to enter your house without a warrant. All he has to do is get a gamewarden . No warrants necessary with them. "well we thought they had illeagal game meat in their residents. Turns out they were growing marijuana" (hypothetical quote) There are many ways you can get busted. Just do everything to ensure you dont. Peace
Probably the same people with those stupid 'get out of jail, free' disclaimers in their sig lines. LOL Delusional thinking. Wet
probable cause is all that is needed. if a cop can smell it or see it... he can bust the door down and fuck your world up.