Groomsmen

It's the bride's privilege to ask her wedding party to dress a certain way for her wedding. It's tradition. She can tell them what jewelry and shoes to wear, too. She can even ask everybody to wear their hair up, or down, if she's super picky. But she absolutely, positively CANNOT ask anybody in her wedding party to alter their physical characteristics in any way.
A simple suit can go a long way -- maybe even until death do you part.