、。
I'll let you know my decision after I've consulted with my lawyer.
Literal
Lawyer [with-と] consulted after-で, decision [obj-を] honorable-inform (polite).
Several keigo pieces. お知らせする is a humble-form (kenjōgo) version of 知らせる ('inform, let know'), using the お + stem + する pattern. Paired with the polite ~します, it marks the speaker as humbly performing the action toward the listener. ~た後で ('after X') is the temporal 'after.' 相談する with と (mutual) rather than に (one-way) is characteristic of professional consultation.