Do (Maryland) police officers always have the right to give a breathalyzer test?

I know that under Maryland law, any person driving a car who gets pulled over has to submit to a breathalyzer test if requested. But is there any law that requires a person on the street to do so? We can assume that there is alcohol in the vicinity, but no direct evidence that the particular (underage) person has posession of any alcohol or has been drinking.

If the underage person is not driving … why would the officer need to use a breathalyzer?

All the breathalyzer will do is give the level of intoxication … not required for a minor in consumption conviction! The officer has reasonable suspicion, and can stop the person, question them (while doing so he’ll also get a smell of the subject’s breath). That’s all the officer needs to give a minor in consumption citation, the smell of alcohol on the person’s breath and proof that they are not 21 or over.

The officer does not need to prove measurable blood alcohol level, the officer does not need to prove intoxication. The breathalyzer would not be necessary in this case.