Ariston by Ruby Lionsdrake

An undercover Star Guardian agent sworn to enforce the law.
A U.S. marine turned galactic pilot, inadvertently breaking the law.
Trapped on a mysterious planet full of dangerous ruins, these two enemies must work together—and deal with their growing attraction—as they struggle to survive.
It’s been two years since delegates from the Confederation visited our solar system, pointing out a wormhole that leads into the rest of the galaxy. Former Marine Michelle “Mick” Saunders was one of the first people from Earth to acquire a spaceship and venture out among the stars. Still haunted by the devastating event that prompted her to leave the military, she’s led a lonely life of late, and longs to find something greater out there.
But for now, she has a spaceship to pay off, so her longings must be set aside. When an Earth corporation wants to send a team of researchers to a uninhabited planet full of ancient human ruins, she accepts the job of transporting them. Little does she know that someone else has a claim on the planet, and that there’s a reason it isn’t inhabited anymore.
When Mick runs into a Star Guardian, one of the fierce warriors that enforce Confederation laws, she realizes she should have asked more questions before accepting the mission. A lot more questions. Even though the hunky Ariston is someone she would rather date than fight, he doesn’t look like one to be swayed from his duty by a flirty smile. Instead, he’s determined to arrest her.
Ariston, a Star Guardian placed under cover on a salvage ship suspected of illegal activities, hasn’t known contentment since he lost his wife years ago. But he’s not looking for anyone new. Especially now. He has evidence to gather and a rogue crew to turn in. There’s no time for distractions, definitely not in the form of an Earth woman trespassing on a protected planet.
But Mick, a fighter and a beauty, intrigues him. Despite his certainty that he shouldn’t get involved, he finds himself wanting to protect her from the dangers of the ruins, as well as the salvage crew plotting to capture her vessel. His mission would have been daunting even without extra complications, but now, he must choose between his duty and the woman rousing feelings within him for the first time in years.