How can laws ment to maintain personal safety be constitutional?

RLTW: How can laws ment to maintain personal safety be constitutional?
Where do legislators get the power to make laws such as ones that force a person to wear a seatbelt or not allowing the sale of fireworks to people over 18?

I can see why there are laws to make us safe from others ex: no speeding because you might hurt someone else) but if your old enough shouldent you, not the government be in charge of your safety?

Answers and Views:

Answer by WHAT SZ DEPENDS DO MCCAIN WEAR?
THATS A GOOD QUESTION AND IT GOES TO SHOW YOU THAT ITS ABOUT THE STATES MAKING MONEY BECAUSE IF THEY REALLY CARE ABOUT PRESERVING OUR LIFE THEN SMOKING CIGARETTES KILLS MORE PEOPLE THAN SUICIDE HOMOCIDE CAR ACCIDENTS DRUG ABUSE AND ALCOHOL PUT TOGETHER. BUT WE AS CITIZENS VOTED THEM IN AND LET THEM BULLY US.