A Florida attorney who represents the billionaire Marshall family, which owns a 16% stake in Koch Industries, will have to face a lawsuit in Texas alleging his letters to the wealthy multinational corporation's CEO were defamatory to one Marshall family member.

Lawyer Edwin Hunter argued that a probate court in Harris County, Texas, did not have jurisdiction over him since he lives in Florida. But Houston's Fourteenth Court of Appeals rejected that argument, listing examples of Hunter advising Marshall family members about legal matters in Texas.

The appellate court's ruling means that Preston Marshall, one of the sons of heiress Elaine T. Marshall, will be able to proceed on his claims that Hunter's two letters to Charles Koch, co-owner, chairman and CEO of Koch Industries, disparaged and defamed him.

Justice Meg Poissant wrote the Fourteenth Court's opinion in Hunter v. Marshall, joined by Justices Ken Wise and Kevin Jewell.

In addition to Hunter, Preston Marshall sued his mother and the estate of his father, E. Pierce Marshall, and other defendants. The dispute arose over shares in a company that Preston Marshall alleged his mother had promised to him, before allegedly breaching her fiduciary duties by not transferring the shares. The ruling shows Preston Marshall also objected to his termination from the family's Houston-based staffing company, Maropco, which has since shuttered. Preston Marshall claimed that Hunter, the family's longtime trust and estate lawyer, assisted in the breach, and breached his own duties to Preston Marshall.

The plaintiff claimed that Hunter in 2015 wrote two letters to Koch that amounted to "a screed misrepresenting plaintiff's actions and attempting to portray him as a ne'er-do-well" because of a dispute with his brother, the opinion said. The letters disparaged and defamed Preston Marshall, he claimed, in retaliation for his demands and lawsuits, among other things.

The appeal before Houston's appellate court had to do with whether the probate court had jurisdiction over Hunter, who claimed he resides in Florida and Utah, and doesn't do business in Texas.

But the trial court found it did have jurisdiction, because Hunter is licensed in Texas, and he does business in the state. For example, he has traveled to Texas to advise the family about a dispute in Texas, and participated in the settlement of that case. Hunter had also given legal advice directly to Preston Marshall in Texas about trusts and estate planning. On a side note: Hunter had also advised the Marshall family about past litigation by model and actress Anna Nicole Smith, who died in 2007, over the estate of her deceased octogenarian husband, J. Howard Marshall, the opinion said.

The opinion said Preston Marshall had met his burden to show his claims arose from Hunter's contacts in Texas. The court ruled that Hunter had failed to demonstrate that evidence was insufficient to establish jurisdiction.

"The trial court did not err in concluding it could exercise specific jurisdiction over appellant," the ruling said.

Hunter's attorney, Holland & Knight partner Brad Hancock of Houston, didn't immediately return a call or email seeking comment. Neither did Preston Marshall's counsel, Susman Godfrey partner Max Tribble of Houston.

Read the opinion: