How much authority does a security guard have?

Here's an example of a situation (one I was in). Me and some friends wanted to go to a party at these apartments right off campus but the apartments complex has a sign in policy and limits the amount of guests someone may have in their apartment. Me and 5 others couldn't get in so someone came and let us in through back doors. As we were walking down the hallway two security staff yelled at us to stop. My specific question I guess is, could I have just left? Did we have to stay and talk to them or could we all have just walked away? They also asked us for I.D. I did not give them mine.

I am in that Industry and have been since 1992.
Ok, The only authority a Security Officer has in Texas is no more than that of a Private Citizen, Now in your situation, they could not physically stop you, if you stopped, it was your choice to stop, however, if you continued on, the consequences would not go well for the person who's apartment you are visiting, and possibly for you, for if you failed to stop, as this has happened to me at an Apartment Complex, when the person refused to stop, I simply called the Police and they took it from there, and it was my decision to have the Police, escort that Individual off the property with a Criminal Trespass warning.

Now in the case of an Armed Security Officer, It depends largely on what he/she is guarding, in most cases, the weapon is used only as a last resort in a case when the only option to keep from being killed is to implement the use of deadly force.
Now this changes for some private security firms that Guard a Nuclear Plant, these Guards will shoot on site anyone attempting to violate the intergrity of that Nuclear site, after all, we are talking about Plutonium the most dangerous subtance known to man (argueably)

E-mail me for any additional questions.

they have about as much authority as an empty jar of mayo..they are there to maintain the environment and be the first to report to the police, fire, EMT, etc..they shouldn't be muscling you around.

First of all, what kind of place was this?? Who would rent an apartment that would try to dictate the number of guests allowed? That just seems ridiculous.

Second, I think it varies by state. I did some research in SC when two bodyguards watched my brother get beat up by 10 kids.

I would say, they have no authority over you, but they have authority over the building and could make you leave.

if you are on their site with no id (which is the norm) you can be classed as an intruder/tresspasser. if you are part of there campus, and you refuse to show id (and it is rule to do so) then youcan be disciplined for not showing your ID. imagine if they allowed anyone onsite, you could end up having an american style slaughter???

they are doing the jobs they get paid for, give them some slack, and remember, to get respect, you have to earn respect. im in uk by the way.

It depends on the state laws where you live and the situation. Generally;

John Doe walking security at a warehouse after hours, very little authority.
A off duty cop working security at an event has all the authority of a police officer.
A security person for Blackwater or Wackenhut can shoot you dead and get away with it.

Security guards have the right to detain you, if they believe a crime has been committed.

In your case, that's trespassing.

They may detain you, only for a reasonable amout of time needed to investigate and to wait for law enforcement to respond.

They have the right to do a pat down, to check for weapons and to restrain you.

But only on the property, they are licensed to be security guards at.

This varies state to state. In two states security guards have full "police" authority while on clients property, in most states guards have the same authority as a private person. Also in most states a licensed security guard may act as "owner of agent" of the property they are guarding.

What this means to you: The guard may act as if he owns the place, and just like the owner, may force you to leave or have you arrested. Also in most states the guard my physically arrest you him/herself (private persons arrest.) The difference between a detention and arrest is really silly in the fact that in both cases you are held against your will by another.