Are the Beatitudes a law or an announcement? When it says, “Blessed are the poor in spirit” does that mean, “Okay, better go out and be poor in spirit!” or “Good news for spiritual losers! The Lord is going to save you”?
The character of the Beatitudes is more of an “announcement” than a “law,” to use your terminology. But “announcement” does not really reflect the sense either. It is important to see that this whole section of Matthew is introducing the character of the Kingdom. In fact, the whole of Matthew’s gospel has a dispensational character. That is, it presents the Lord Jesus as King and so contains many elements that relate to the Millennial Kingdom. Some incorrect interpretations of passages in Matthew are common in Christendom because the expositor has failed to keep this in mind.
The particular example you mention is an encouragement to those who have felt the distress of the rejection of the King. They will, in the end, find their place in the Kingdom. The whole verse you refer to is, “Blessed are the poor in spirit, for theirs is the kingdom of heaven” (Mt. 5:3). Like many of the Beatitudes, this does not directly refer to those of us in the present Church period. Rather, it has a direct application to those who suffer during the tribulation period. A similar verse is, “But the one who endures to the end will be saved” (Mt. 24:13). In both cases, the subject is that those who endure the persecution through the tribulation will be saved to live in Millennial blessing. Nevertheless, we can gain comfort from these verses because the same principles apply to us. In this example, we can see the analogy to 2 Timothy 2:12a: “if we endure, we will also reign with him.” The third Beatitude, which reads, “Blessed are the meek, for they shall inherit the earth” (Mt. 5:5), is similar to the one you mention. It is not true that we shall inherit the earth. Yet, it is easy to see that the general truth of it is again similar to the verse from 2 Timothy. Similarly, many of the admonitions and encouragements are applicable to us.
When reading Matthew’s Gospel it is important to keep in mind its dispensational perspective. The Kingdom is being presented, but the King is rejected. So the Kingdom in its public display is delayed. It will be established in the future. In the meantime, the Kingdom exists in a “mystery” form. That is, the King is absent, so there is no real dominion on earth. However, the subjects of the Kingdom remain but are in different relationships. Christ is our Lord, not (strictly speaking) our King. A very significant verse in this regard is John 18:36. In this verse, Jesus is standing before Pilate who represents the political and military leadership in the world. If Christ’s Kingdom were to be established in the world it would have required the disciples to fight for Jesus’ life. But, the King having been rejected, the Kingdom was now to exist in a different form, at least until the rightful King returns and people say “blessed is he that comes in the name of the Lord” (Mt. 23:39). Some have missed the significance of the words of the Lord before Pilate and seek to establish the Kingdom by political efforts. The hope and activities of the Assembly are in quite a different direction.
Now, although I think you meant the phrase “spiritual losers” in jest, it deserves comment because we may actually feel this way sometimes, even if we don’t say so. The Lord Himself is described as “gentle (or, “meek”) and lowly” (Mt. 11:29; see also Isa. 57:15; 66:2). The phrase, “poor in spirit” does not at all have the sense of “spiritual loser.” Rather, it refers to those like Daniel in Daniel 9:3–19 who truly mourn over the spiritual condition of God’s people and people in general.
 Please do not misunderstand me here. I do not mean to disparage songs or thoughts regarding Christ as King. Rather, I hope that we appreciate the nearness we have been brought into. The King-Servant relationship is much inferior to the Friend-Friend (Jn. 15:15) or Husband-Wife relationship (Eph. 5:32). We best serve Christ not out of obedience to commandments but out of our love and devotion to the One who died and is risen for us (1 Jn 4:19).