Constantin primarily works with construction and contract law, as well as dispute resolution. He assists large and medium-sized companies in the construction, civil engineering, and industrial sectors. The cases he has experience with are large, complex, of long duration, and involve significant amounts of information.

In 2024, Constantin wrote his master’s thesis on remuneration adjustments for extraordinary price increases of input factors in land-based construction projects.

As a student, he specialized in dispute resolution and won ELSA Tromsø’s moot court competition, where he was named best oralist several times.