The Fourth Amendment to the United States Constitution protects you against any illegal or unlawful seizure (arrest) by the government. A temporary non-custodial traffic stop turns into an "arrest" when a reasonable person in your position would think that the traffic stop was no longer temporary.
What is an "arrest"?
Certainly, when you have been put in the back seat of a police car with no interior handles to open the doors, or if you have been handcuffed and are no longer free to leave, you are under arrest. In most states, when the police draw weapons and point them at you, you have no expectation that this will be an ordinary, temporary traffic citation, while this is not true in all circumstances. Whether or not you are under arrest depends not upon the opinion of the officer, but upon existing facts and circumstances that support a normal person's subjective sense of lack of freedom.
"Arrest" in a DUI-DWI case
The rules outlining what constitutes sufficient "probable cause" or reasonable grounds for a custodial arrest for DUI-DWI vary from state to state. Whether or not there was sufficient probable cause or reasonable grounds for your arrest for DUI-DWI will depend on your state's case law, statutes and constitution, plus the circumstances surrounding your arrest. Having the smell of alcohol on you alone is typically not enough "probable cause" for a custodial arrest for impaired driving, unless you are under age 21 and alcohol is a prohibited substance for you to possess. In Texas, where no "open container" law exists, just because the police see the driver with an open bottle of beer in his hand, it is not by itself a sufficient reason to stop you. This is why your DUI-DWI specialist attorney will need to know all of the minor details of your arrest.