The Catechism of the Council of Trent has this to say on the matter of invoking the saints.
CCT 2010 In explanation of this Commandment it should be accurately taught that the veneration and invocation of holy Angels and of the blessed who now enjoy the glory of heaven, and likewise the honour which the Catholic Church has always paid even to the bodies and ashes of the Saints, are not forbidden by this Commandment. If a king ordered that no one else should set himself up as king, or accept the honours due to the royal person, who would be so foolish as to infer that the sovereign was unwilling that suitable honour and respect should be paid to his magistrates? Now although Christians follow the example set by the Saints of the Old Law, and are said to adore the Angels, yet they do not give to Angels that honour which is due to God alone.
CCT 2011 And if we sometimes read that Angels refused to be worshipped by men, we are to know that they did so because the worship which they refused to accept was the honour due to God alone. Rev 19:10; 22:9
CCT 2012 It Is Lawful To Honour And Invoke The Angels
CCT 2013 The Holy Spirit who says: Honour and glory to God alone 1Tim 1:17; Exo 20:12; Lev 19:32, commands us also to honour our parents and elders; and the holy men who adored one God only are also said in Scripture to have adored, that is, supplicated and venerated kings. If then kings, by whose agency God governs the world, are so highly honoured Gen 23:7; 2Ki 24:20; 1Ch 29:20, shall it be deemed unlawful to honour those angelic spirits whom God has been pleased to constitute His ministers, whose services He makes use of not only in the government of His Church, but also of the universe, by whose aid, although we see them not, we are every day delivered from the greatest dangers of soul and body ? Are they not worthy of far greater honour, since their dignity so far surpasses that of kings?
CCT 2014 Add to this their love towards us, which, as we easily see from Scripture Dan 10:13, prompts them to pour out their prayers for those countries over which they are placed, as well as for us whose guardians they are, and whose prayers and tears they present before the throne of God Tobit 12:12. Hence our Lord admonishes us in the Gospel not to offend the little ones because their angels in heaven always see the face of their Father who is in heaven. Matt 18:10
CCT 2015 Their Intercession, therefore, we ought to invoke, because they always see tile face of God, and are constituted by Him the willing advocates of our salvation. The Scriptures bear witness to such invocation. Jacob entreated the Angel with whom he wrestled to bless him; nay, he even compelled him, declaring that he would not let him go until he had blessed him. And not only did he invoke the blessing of the Angel whom he saw, but also of him whom he saw not. The angel, said he, who delivers me from all evils, bless these boys.
CCT 2016 It Is Lawful To Honour And Invoke The Saints
CCT 2017 From all this we may conclude that to honour the Saints who nave slept in the Lord, to invoke them, and to venerate their sacred relics and ashes, far from diminishing, tends considerably to increase the glory of God, in proportion as man's hope is thus animated and fortified, and he himself encouraged to imitate the Saints.
CCT 2018 This is a practise which is also supported by the authority' of the second Council of Nice, the Councils of Gangra, and of Trent, and by the testimony of the Fathers. In order, however, that the pastor may be the better prepared to meet the objections of those who deny this doctrine, he should consult particularly St. Jerome against Vigilantius and St. Damascene. To the teaching of these Fathers should be added as a consideration of prime importance that the practise was received from the Apostles, and has always been retained and preserved in the Church of God.
CCT 2019 But who can desire a stronger or more convincing proof than that which is supplied by the admirable praises given in Scripture to the Saints? For there are not wanting eulogies which God Himself pronounced on some of the Saints. If, then, Holy Writ celebrates their praises, why should not men show them singular honour? Sir 44, 45, 46, 47, 48, 49; Heb 11
CCT 2020 A stronger claim which the Saints have to be honoured and invoked is that they constantly pray for our salvation and obtain for us by their merits and influence many blessings from God. If there is joy in heaven over the conversion of one sinner Luke 15:7,10, will not the citizens of heaven assist those who repent? When they are invoked, will they not obtain for us the pardon of sins, and the grace of God ?