It is a key point from the legal viewpoint.
Police are allowed to enter a premis under the following situations:
1) they have a warrant
2) they have probable cause (knowing of or observing a violation of law)
3) they have exigent circumstances (someone in danger)
4) they have the owners permission
Given the fact that the cops attempted entry and were rebuffed, that means the cop knew that they did not have any of the above 4 conditions.
How about a reasonable suspicion that someone underage was consuming alcohol and asking for ID?
I've been looking for a copy of the suit, to see if it has more detail. So far all I find is the AP story repeated on various propaganda outlets.