[@Maxwell57] They could at least try to open the gates of Moria to no avail. Maybe the gates are open since Frodo and his fellowship have already passed through it? (I can't remember if the gates closed behind them or not.) 

For your information, the writing above the gate says [color=00aeef]"The Gates of Durin, Lord of Moria. Speak Friend and enter."[/color] Frodo then says [color=ed1c24]"It's a riddle. What's the Elvish word for friend?"[/color] Gandalf responds by saying [color=fff200]"Mellon."[/color] The doors open, and they enter with caution. There are a couple plausible ways the group could enter, be it by mistake or deliberately.