The "letter of the law" is that a gift to the Church is just that - to the Church. If the gift is to a person, rather than to a recognized charitable organization, it does not qualify as a "Contribution" for the contributor.
Is the Treasurer correct? Yes. No question. But, the issue of correctness is not whether the gift should, or should not, go to the Pastor (If this money does NOT go to the Pastor, the intent of the giver has been betrayed, and that giver's confidence in the Church may be compromised.).
The real issue is whether the Church can issue a receipt, recognizing the gift as a "Contribution" from the contributor. The "letter of the law" is not to prevent that money from going to the Pastor, but to prevent the contributor from taking a "Contribution" deduction for a gift that was not intended for the "Church" but for a person (who does not qualify as a charitable organization).
The resolution, in my opinion:
1. The Church should NOT issue a receipt to this contributor that would include this "special" gift for the Pastor. Whether that contributor deducts the amount on their income tax return is not the Church's, or the Pastor's responsiblity to control. (A receipt that does not include this money exercises the limit of Church control over the contributor.)
2. Take action, as a Church Board, to give the Church Board authority to redirect any "specifically designated gift" that comes in to the Church in the future. The problem with the present situation is that the Church is bound by the labeling and intent of the giver. (The Church would be remiss in NOT passing this current "gift for Pastor" to the Pastor. This does not mean the Church needs to approve of this gift as a legal "contribution" to the Church.) There is currently no Church Board authority to "override" the expressed intent of any contributor.
3. A long-term solution is to add "special" funds to the single "general fund" that most Churches use for accepting offerings. My suggestion is for General Fund, Building Fund, Pastor's Fund, Missionary Fund and any others deemed appropriate by the Board. The congregation has the freedom to contribute to any of these funds or to spread their tithes and offerings among them. The Church Board has the authority to redirect any of the funds for other purposes if it deems this a necessity. This needs to be balanced by a responsible accounting to the congregation of the handling of the funds involved - in the annual report of no where else. This gives the Church the freedom to include these contributions in the receipts provided to contributors AND the freedom to redirect funds as necessary to (1) meet periodic bills that need to be paid and, (2) meet "special" needs as they arise, e.g., a hardship in the Pastor's family. How to do this - several options: (1) provide envelopes in the pews in which contributors can put funds and label the envelopes as they see fit - for which "fund(s)" they want the money to go to, (2) encourage folks to designate on their check(s) the purpose for this gift, or (3) as I have seen in some Churches, eliminate the plate offering (a giant step of Faith) and simply provide a multiple pocket depository in the building for folks to put money into different pockets or slots labeled for the various funds.
One further thought, as SkyHawks has alluded to - this "gift" is not part of the compensation, for services rendered, from the Church and is to be handled by the Pastor as just that - a gift - not subject to income tax (The amount of the gift is not the issue - the characterization ((purpose))of the money is the issue.) If money is passed through the Pastor's Fund during the year, it WOULD be part of the compensation for services package and includable in the Pastor's W-2.