Open House but

Legally, no. But it's always appropriate, classy, and preferred for them to say something like "We have an approved offer, and are now soliciting back-ups"

What really annoys me is when I make an appointment to see a place (not a general open house, but a private appointment), and the broker does not tell me this point on the phone then and there (assuming they know it to be true). I schlep in a cab or subway, get there, and after looking at the place carefully and asking questions (if I'm interested) only at the end does the broker say "by the way, we have an accepted offer". If I had known that on the phone initially, I probably would have chosen not to spend the time and money going back and forth to see the place in the first place. I've really let brokers have it in the past when they've pulled that stunt.

mj- I fell your pain. the FIRST thing I always ask an agent now is "IS THERE AN ACCEPTED OFFER?".

I am asking in this particular case because imagine this scenario:
The sell side pressured the buy side (and their attorney) to get a contract signed before the weekend -gave only 2 days to get everything done- read minutes, make changes, etc. The agent specifically said if the contract got signed, the seller would sign, and there would NOT be an open house. The buy side signed and gave the deposit. At 5 pm on Friday, the agent listed the open house and the seller hasn't signed.

OP you're still at the offer stage until the seller signs.

But, you are the master of your offer. You can choose not to be held hostage.

Ask your attorney to call their attorney and say, if a signed contract is not received by X date and time, the offer is withdrawn.

You should also keep looking until both parties sign.

My feeling is that 2 days is simply not acceptable.

It sometimes takes the managing agent more time than that to get the information to potential buyer. In addition, any place I purchase must undergo a standard review (takes about an hour) by a building inspector. It usually takes me 2-4 days to schedule that.