The DP World Tour is set to ban duel membership between them and LIV Golf for 2027. Why are they doing it? We will try to answer this.

Unlike the PGA Tour (which suspended LIV players from the start in 2022), the DP World Tour previously allowed some members to compete in LIV events under conditions. Players who joined LIV without releases faced fines.

In 2026, the tour granted conditional releases to about nine players, including Tyrrell Hatton, and later Jon Rahm. In exchange, they paid prior fines, withdrew appeals, and committed to extra DP World Tour events and promotional duties. Those releases were explicitly limited to 2026.
The reason the DP World Tour is doing this is to protect their membership model, tour rules, and overall their business as LIV 2.0 undergoes restructuring amid bankruptcy. CEO Guy Kinnings stated players “need to make a choice” and must abide by rules “there to protect our tour.”
LIV is restructuring amid bankruptcy and loss of Public Investment Fund support. The new model features fewer events (around 10), lower purses, and (here is the big kicker) player equity ownership. DP World Tour officials view this as incompatible with their member owned structure, as it would incentivize players to prioritize LIV over full commitment to DP World Tour events.
This also effects Ryder Cup eligibility since only DP World Tour members can play for Europe. It’s a very real choice that DP World Tour and LIV players have to make.
TL;DR:

The DP World Tour is enforcing exclusivity to safeguard its regulations, member focus, and commercial position now that LIV’s structure has changed and the previous temporary accommodations have expired.