CAN I make an offer to Homeowner that has Realtor Involved?

[Yader Nicaragua Gil]

Hi BP community, I recently got a lead looking to sell us his house but after researching we found out was on the MLS and has a realtor involved, so We told him that we couldn't help him but he told me that he could cancel the contract with the realtor anytime if our offer is good enough.

So my question is How can I do this type of transaction ?

Can I give him an offer ? and if their is no legal consequences? 

THANK YOU!