Upvote:7
The answer to this question probably depends somewhat on the reason for the visa revocation. For example, if the visa was revoked because your client was found to be inadmissible to the US for some reason, applying for entry using the Spanish passport does not remove any grounds of inadmissibility, and your client is still inadmissible.
If your client's purpose of travel is permitted under the Visa Waiver Program, he can travel to the US to apply for entry using the Spanish passport if he applies for and is granted ESTA authorization. In the course of the ESTA application, the system will ask about other passports. Trying to use the other passport to conceal the prior visa refusal is a bad idea; such deception will almost certainly be uncovered. Even if the ESTA authorization is granted, the officer at the border can still deny entry, which will almost certainly happen if deception is suspected. The best chance of avoiding refusal of entry at the border will be to apply for a new visa.
While this concerns visa denial rather than revocation, it is nonetheless relevant; it is taken from the State Department's page on the VWP:
I was denied a visa under section 214(b). May I use the VWP?
A recent visa refusal for any reason could result in denial of ESTA authorization, additional review at the port of entry, or denial of admission to the United States. If you are uncertain if you qualify for VWP travel, you may choose to apply for a visa.