Visitors Visa Denial

Hey,

My sister and brother-in-law are booked to travel to the US in May.  We knew my BIL would need a visa due to a 25-year-old offense.  He had also applied for a visa previously and been approved (when he traveled to my marriage in the US).  Note: there has been no further offense since the approval of that visa 12 years ago

He visited the embassy last week after applying and was denied due to not checking a box on the ETSA (or so they said).  My sister is filling out the paper work again and before she paid the earliest date appears to be July.

Can anybody offer any advice and/or have any lawyer contacts in London who may be able to assist in this matter?

Thanks

Steve