Complex sentence: The chief legal barrier to its removal were the terms of the trust created at the Pillar's inception, which gave the trustees a duty in perpetuity to preserve the monument, and successive Irish governments failed to bring in legislation that would override the trust.
Split into simpler sentences: The chief legal barrier to its removal were the terms of the trust created at the Pillar's inception, which gave the trustees a duty in perpetuity to preserve the monument. Successive Irish governments failed to bring in legislation that would override the trust.