Earl of Argyll
Although he had finally regained the title of Earl and much of his inheritance, Argyll's affairs were still encumbered by debt. His harsh treatment of his own debtors and apparently unscrupulous use of his hereditary and other offices gave him a poor reputation amongst some contemporaries. He was also involved in ongoing litigation with Montrose, although they were reconciled by February 1667. Montrose visited Argyll at Inveraray in August, and in March 1669, Argyll travelled to Perthshire from Inveraray to attend his funeral, becoming guardian to his son.
On 29 April 1664, Argyll was placed on the Scottish Privy Council. During 1664 and 1665, he was regarded as one of the chief members of John Maitland, 1st Duke of Lauderdale's party, Lauderdale being godfather to one of his children.
During the mid-1660s, Argyll remained for the most part at Inveraray Castle, exercising his hereditary office of grand justiciar of the highlands, and mediating between highland chiefs. He devoted a great deal of attention to planning the gardens at Inveraray, and was particularly interested in tree raising and planting, seeking advice from John Evelyn on the subject. His plan was to stock the gardens themselves with fruit trees, and to thickly plant ornamental trees around so that the house had the appearance of rising out of a wood: he had a particular fondness for elms. He also devoted time to the production of salt herrings and distilling whisky, hoping to create an export trade to England, and sent samples of his products both to Lauderdale and to Charles II.
Although Argyll had some involvement in the religious disputes of the period, acting to disarm the Covenanters in Kintyre, he was regarded as one of the moderates on the Privy Council. There remained opponents amongst the other council members, particularly James Sharp, the Archbishop of St Andrews. This opposition to Argyll surfaced in an attempt to challenge his formal restoration to his hereditary offices in October 1666. It again appeared when the Pentland Rising took place: Sharp would not allow Argyll's forces to participate, fearing that he and his men would join the rebels. After their rout the leaders of the rebels tried to reach the west coast to cross over to Ireland, and on 14 December, Argyll received instructions from the Privy Council to capture them if possible.
In 1667, Argyll received a new charter of all his lands and hereditary and other offices from Charles II. On 3 August, he was appointed, with Atholl and Seaforth, to have the oversight of the Highlands, which were then in a disturbed state. He was still on good terms with Lauderdale and backed him against the other main party on the Privy Council, headed by the 7th Earl of Rothes: in September he wrote to Lauderdale urging him to secure Rothes's resignation of the commissionership.
In May 1668, Argyll's wife died; his personal letters at the time describe his feelings of desolation at her death. In October 1669, Lauderdale visited Scotland as high commissioner. Argyll was aware that Elizabeth Murray, Lady Dysart, who was shortly to become Lauderdale's second wife, was using her influence against him, and made a point of personally attending Lauderdale at Berwick. At the opening of the Scottish Parliament, he carried the sceptre. One of the issues debated by this parliament was to formally ratify the reversal of Argyll's father's forfeiture. This was opposed by the 11th Earl of Erroll and other of Argyll's creditors, but Lauderdale pushed the ratification through by deciding it was not to be voted on and a matter for the King alone to decide.
On 28 January 1670, Argyll married for the second time, to Lady Anna Mackenzie, dowager Lady Balcarres. This caused a brief souring of his relationship with Lauderdale, who thought that his godson, the young earl, would be adversely affected by the marriage.
Argyll was opposed to further persecution of the western Covenanters but was ordered by the privy council to suppress the conventicles in his jurisdiction. On 11 July 1674, he was made an extraordinary lord of session. He had in May been made a member of the committee for public affairs appointed to put down conventicles; in 1677, he was still supporting moderate measures.
He quietly rebuilt his alliance with Lauderdale, and the daughter of the second Duchess of Lauderdale married his eldest son, Lord Lorne. On 10 October 1678, he received a commission to seize, with the aid of three companies, the Isle of Mull, where a vicious turf war had been going on between Argyll and the McLeans since 1674. It took until 1680 for him to gain possession.