I think you're confusing the terms "reasonable suspicion" and "probable cause".
Reasonable suspicion is a reasonable presumption that a crime has been, is being, or will be committed. It is a reasonable belief based on facts or circumstances and is informed by a police officer’s training and experience. Reasonable suspicion is seen as more than a guess or hunch but less than probable cause.
Probable cause is the logical belief, supported by facts and circumstances, that a crime has been, is being, or will be committed.
You can be detained, checked for weapons and questioned by Police under "reasonable suspicion". Any weapon found, whether legally owned or not, can be secured by the cop until you are released or, if probable cause exists, arrested.
The Police can't arrest you unless there is "probable cause".